1. Field of the Invention
This invention relates to a light emitter. In particular, it relates to light-emitting diode arrays (hereafter abbreviated as "LED arrays") used in the solid state light sources of photo-copiers, facsimile machines, and the like.
2. Description of the Related Art
An example of a conventional LED array is shown in cross-section in FIG. 1. In the drawing, reference numerals 101, 101 ... represent LED chips arranged in a straight line on a glass epoxy printed circuit board (hereafter abbreviated as "board"). The chips are arranged at equal distances from each other. Moreover, immediately above this group of LED chips and parallel to them, a cylindrical lens 103 is secured to board 102 by a holder 104, which doubles as a reflector. Incidentally, a light receiving surface 105 is mounted above cylindrical lens 103 and separated from it by about 30 mm.
In order to obtain a specified illuminance from this conventional LED array, the individual chips of this group of LED chips are arranged at equal spacings of, for example, 5mm apart, as shown in FIG. 1. Since the illuminance distribution C declines markedly at both ends of the array, as shown in FIG. 2, the region of even illuminance, referred to as the effective illuminance region A, is shorter than the overall length B of the LED array.
Since the illuminance distribution C decreases at the ends in an LED array of conventional construction, as mentioned above, the overall length of the LED array needs to be longer than the required effective illuminance region. However, there is a great problem that, in order to make a compact shape for machines such as photo-copiers and facsimile machines in which LED arrays are used, where there are no chips, the gap being in many cases it is difficult to obtain the desired characteristic the overall length of the LED array is shortened and because of space restrictions inside the machine in which the LED array is installed.